what is the `A-` binding?

Question

On Emacs, if I type C-h, b a list of keybinds come up, including:

what is A- and how do I access it?

Answer 1

A- is the Alt modifier. Which, for clarity, is almost definitely not the key labelled 'Alt' on your keyboard -- that's recognised as the Meta modifier.

Most people simply don't have this modifier key. It's relatively common for people to configure Super and Hyper modifiers on modern keyboards but, probably on account of the potential for confusion, one doesn't tend to hear about people using the Alt modifier in Emacs these days. (It was useful on keyboards which had an 'Alt' key and a 'Meta' key, though.)

If you have a need, you can invoke the Alt modifier like so:

C-x@a

Followed by whichever key you wish to be modified. In your examples: *

Function key map translations Starting With C-x @:
key             binding
---             -------

C-x @ S         event-apply-shift-modifier
C-x @ a         event-apply-alt-modifier
C-x @ c         event-apply-control-modifier
C-x @ h         event-apply-hyper-modifier
C-x @ m         event-apply-meta-modifier
C-x @ s         event-apply-super-modifier